Process of treating iron or steel rods or wire



Mar. 3. 1925. 1,528,245

F. M. CRAPO PROCESS OF TREATING IRON OR STEEL RODS 0R WIRE Original Filed Dec. 10, 1923 I a s A TTORNEY.

Patented Mar. 3, 1925.

UNITED STATES PATIENT OFFICE.

rannnalox M. CRAPO, or MUNCIE, INDIANA.

PROCESS OF TREATING IRON 0R STEEL RODS 0R WIRE.

Original application filed December 10, 1923, Serial No. 679,650. Divided and this application filed February 27, 1924.

To all whom it may concern.

Be it known that I, FREDERICK M. CRAPO, a citizen of the United States, residing at Muncie, in the county of Delaware and State of Indiana, have invented a new and useful Process of Treating Iron or Steel Rods or \Vire, of which the following is a specification.

The primary object of my present invention is to produce a corrosion-resisting surface on iron or low-carbon steel wire, whether or not such surface is subsequently coated, as with zinc; and to providena sun face to which a zinc coating if subsequently applied will adhere 'firmly.

A further and most important object is to simplify, cheapen, and shorten the process of cleaning and/or annealing at any stage of the manufacture of iron or steel wire. This cleaning and/or annealing may be used as a preparation for coating, as with zinc; or as a mere independent operation, without relation to immediate coating, or to any coating at all.

It is a further object to do these things without adversely affecting the mechanical and electrical properties of the wire, such as tensile strength, elongation, and electrical resistivity.

This present application is a division of my co-pending application Serial N o. 67 9,650, filed December 10, 1923, now Patent No. 1,501,887, granted July 15, 1924.

In accomplishing these results in the preferred way, I pass the iron or low-carbon steel wire, or the rod from which such wire is made, preferably in continuous operation, through a suitable surface-treating bath, to produce the desired surface change. This prepares the surface for the application of the zinc coating, if a zinc coating is subsequently applied, but also produces a. surface which is itself resistant to corrosion. The aforesaid co-pending parent application involves the feature of zinc-coating, but the present application is independent of any subsequent coating.

I am not fully certain. of the action of this surface-treating bath, but the bath I have used with the best success contains carbonizing material, such as a commercial cyanide mixture of any suitable proportions, maintained in molten condition at a temperature advantageously between 1200 F.

Serial No. 695,423.

and 1300 F I believe that this produces a superficial carbonizing action on the ironbase (or ferrous-metal) body, and so produces a relatively high-carbon surface condition. In any event, it has several important actions on the wire orrod. In the first place, it produces some effect on the surface of the iron or low-carbon steel wire or rod that results in the better adherence of a zinc-coating subsequently applied, and causes such coating to have superior mechanical properties," as set forth specifically in my aforesaid co-pending application. In thesecond place, I find that I obtain a very effective annealing of the wire, after it has been drawn partly or wholly to the desired gage; so that it is possible completely to eliminate the usual annealing furnace which heretofore it has always been considered necessary to provide after the wire has been drawn down to a certain size. In the third place, I find that the bath of molten salts, in addition to the surface-treating and the annealing effects, produces a most effective cleaning action; so that it is possible to eliminate or reduce the usual acid treatments, whether of the rodbefore drawing or of the wire after drawing and annealing; though if the wire is subsequently to be coated with zinc, I prefer to retain a short acid bath, or to provide a zinc chloride or other bath, just before the bath of molten zinc, in order to get the desired fluxing action.

Thus by the immersion of the iron-base rod or wire in the aforesaid bath of molten salts I obtain a very effective chemical heattreating, which has many advantages.- By the term chemical heat-treating, I mean the production in the iron-base (or ferrousmetal) body of both a permeative addition by chemical change and a heat-treatment, such for example as annealing and superficial carbonization, both of which occur in my bath of molten salts.

By avoiding or reducing the riod of immersion in acid I practically e iminateloss of iron, for there is substantially no such loss in the chemical heat-treating. Further,-

I believe I avoid the occlusion of hydrogen in the surface of the iron-base body, such as may occur in acid treatment. This may contribute to the production of the surface condition which better resists corrosion if left tion at the end of the operations on the wire, and just prior to coating if a coating 1s to be applied. However, 1t 15 not essential that this surface treatment be at this point in the process; It may be at any earlier point in the process, though then it .may be desirable to produce a second an-.

nealing and cleaning at the end of the drawing operations, on account of intervenin actions on the wire. When such a secon annealing and cleaning is done, it may be either by passing the wire through a second and similar bath of molten salts, in accordance with my invention, or may be in the old way of passing the wire through an annealing furnace or annealing bath and then through an acid bath for cleaning. Thev surface effect which my bath of molten salts produces will follow the wire all the way through the series of dies, or through any part thereof which may be desired; and throu 'h such annealing furnace or bath and acid cleaning bath if they are used.

In consequence, I have found it both possible and desirable to use this annealing and cleaning method even on the original rods, of about one-quarter inch diameter, with which the wire-drawer starts in the manufacture of wire, and to obtain a most effective cle'an' thereby. This makes it possible to eliminate the usual long and somewhat complicated method of cleaning rods prior to drawing. Further, by avoiding the acid pickling which forms part of the usual preparatory process, I largely eliminate the loss of iron and the possibleocclusion of hydrogen already referred to, nd also lessen or eliminate the tendency to come brittle. This preparatory cleaning and treatment in the bath'of molten salts may be' supplemented by one or more subsequent annealm or cleanings, whether in the same or some other manner; but whether or not there is any other subsequent treatment by passing through a bath of inolten salts, this preparatory treatment produces on the surface some effect, robably carbonizing, which persists throng out all the subsequent operations, makes the final wire more resistant to corrosion even if the wire is notv coated,: and

makes it possible to appl 0 e final gage is reached. 5

Thus this treatment of the surface of the v wire in the bath of molten salts produces some sort of a preserving efleet, even if there is -no subsequent zinc-coating. In other words, a wire which has been treated by a betterv zinc In addition, this treatment of the surface of the wire by passing it through the bath of molten salts is. found to have no appreciable detrimental effect on the electrical and mechanical properties of the wire, such as tensile strength, elongation, and electrical resistivity; so that all the advantages of lowcarbon content are retained, and also there are added advan In using thisbath of molten salts, I have found it possible to vary the composition of the bath very greatly. I believe the bath should contain some. carbonizing material, mixed with other. things serving mainly as fillers or diluents. A advantageous mixture which I, have used contains 60% sodium cyanide, 20% sodium carbonate, and 20% sodium chloride. Further, the temperature of the bath may be varied quite considerably, and I have found the process very effective with temperatures ranging from. about 1200 F. to about 1300 F.

The bath of molten salts may be covered with a thin la er of coke, if desired, to lessen exposurc'to te atmosphere and consequent heat loss due to radiation and possible evaporation. This layer of coke also serves partly as a wipe for the wire as it leaves the baltth, thus effecting a reduction in the 10$ of sa s.

The bath is preferably so arranged that the wire remains in it only for a short time. No period of immersion which I have tried for drawn wire has proven too short, even down to seven or eight seconds; but for such drawn wire I prefer an immersion of about fifteen seconds, to obtain a more. complete annealing and a desirable cleaning, as well as the desired surface treatment, and greater permissible tolerance inthe period of immersion and in the temperature of the bath. When the bath is used for rods, which are of larger diameter than wire and are frequently very rusty or covered with scale, a somewhat longer period of immersion is necessary, to permit the removal of the rust and/or scale as well as the chemical heat-treatment, and to permit the larger-diameterbody of the rod to become heated to 'a sufficient degree forigucll: chemical heat-treadtglent. I h

t e accompanying wings, ave illustrated ap aratus for practicing my process and -p ucing my improved product:

Fig. 1 is a longitudinal sectional view show ing diagrammatically an apparatus for surface-treating, annealing, and cleaning a wire by chemically heat-treating it after it. has

been drawn to the desired gage, and shows also means for zinc-coating the wire following such chemical heat-treating though such zinc coating is not part of the invention claimed in the present application and is shown merely to indicate a usual subsequent operation, all in continuous operation; and Fig. 2 is a longitudinal sectional view showing diagrammatically an apparatus for surface-treating and cleaning rods in a continuous process in preparation for wiredrawing.

Referring first to the apparatus shown in Fig. 1:

The iron-base wire 10, of iron or low-carbon steel, is here presumed to have been passed previously through the desired sizing dies, until it has reached the final gage, at which it is to be chemically heat-treated, whether or not as a preparation for coating. Such wire is passed through a tank 11, containing my bath of molten carbonizing salts; and then, with sufiicient interval for some cooling, through aHbath 12 of water for removing any adhering salts. Then, if the wire is to be zinc-coated, it is passed through a fluxing bath 13, of any suitable flux, suchas hydrochloric acid or zinc chloride, and then through a bath 14 of molten zinc, inwhich the wire takes its zinccoating. After the final treatment of the wire, whether or not it is coated with zinc, it passes to the winding reel 15. If desired, and usually it is desirable, a hot plate 16 may intervene between the fluxing bath 13 and the molten zinc bath 14, so that the wire will be substantially dry when it enters the molten zinc.

Thechemically heat-treating bath 11 contains the molten carbonizing salts 17, above referred to, preferably covered by a coke layer 18. These salts 17 are maintained at a temperature somewhat above their melting point, advantageously between 1200 and 1800 F., as by a fire 19 below the bath 11. For carryingoif fumes,-a hood 20 is preferably provided over the bath 11. This bath 11 serves to give the desired surface treatment, which it is the fundamental object of my invention to obtain. It also acts to produce the desired annealing and cleaning; so that the usual annealing furnace may be dispensed with, and so that no acid bath is needed for cleaning, although a short .acid bath 13 maybe used for fluxing if a zinc coating is subsequently applied. F Referring now to the apparatus shown in The rod from which the series of drawing operations starts is passed through awtank 11 containing my bath of molten carbonizing salts; then through'a bath 12' of water for removing any adhering salts; and then to the winding reel 15'. All this is in continuous operation; which continuous operation I prefer for the treatment of both rod and wire, though the feature of con tinuous operation is not essential to my invention save in those claims which specify it. The molten salts 17 in the bath 11 produce a chemical heat-treatment on the rod 10, and effectively clean it; so'that from the reel 15 the rod is ready to go to the drawing dies. The salts 17 in the bath 11 are maintained in molten condition by a fire 19 below; may be covered'by a layer of coke 18, if desired, though that is not necessary; and preferably have a hood 20 above them for carrying off any fumes.

If desired, in order to lessen the time of immersion in the bath 11' of molten salts, the rods 10 may be passed through a bath of molten lead just previous to entering the bath 11'. The molten lead in the bath 25, when that bath is used, serves to heat the rod, so that less rise intemperature of the rod will be necessary in the bath of molten salts, and the period" of immersion in the molten salts may be reduced. The bath 25 of molten lead is thus merely an example of apreliminary heating means for the rod or used whenever desired in practicing my invention; but it is merely a convenient preliminary, and is not essential. It is not shown in Fig. 1.

I claim as my invention:

1. The process of making iron or steel wire, and such preliminary heating may be passing the wire through a molten bath of canbonizing salts to produce an annealing and a cleaning and also a superficial change in the wire.

3. The process of making ironwor stee-l wire, which consists in drawing the w re to a desired-gage, and subsequently passing it through a carbonizing bath of molten salts to anneal and clean the wire in 'the same 11nmersion. A

4. The process of making iron or steel wire, which consists in drawing an iron or low-carbon steel wire to a desired gage, subsequently passing the wire throfih a molten bath of carbonizing salts to pr uce an annealing and a cleaning and also a superficial chan e in the wire, and subsequently drawing the wire to a smal'er gage. v

5. The .process of making iron or steel wire, which consists in drawing an iron or low-carbon steel wire to a desired gage,

subsequently passing the wire through a iii! low-carbon steel wire tllI'Ollll molten bath of 'carbonizing salts to produce an annea'ing and a cleaning and also a superficial change-in the wire.

6. The process of making iron or steel wire, which consists -inpassin an iron or a molten bath of carbonizing salts to produce an anneaing an da cleaning and also a superficial change in the wire, and subsequently drawing the wire to a smaller gage.

7. The process of making iron or steel wire from rod, comprising cleaning the rod and producing a superficial change in the rod by immersion in a molten bath of carbonizing salts, and subsequently drawing wire from such treated rod.

8. The process of making iron or steel wire from rod, comprising cleaning the rod and producing a superficial change in the rod by immersion in a molten bath of carbonizing salts, and subsequently drawing wire from such treated rod, and passing the drawn wire through a molten bath of carbonizing salts toproduce an annealing, and a second clean in and a further superficial change in the am 9. The process of making iron or steel wire, comprising drawing the wire to a desired gage, and at any desired stage in the manufacture of the wire prior to drawing to the final gage chemically heat-treating the wire.

10; The process of making iron or steel wire, comprising drawinga wire to a desired gage, and at any desired stage in the manufacture of the wire prior to drawing to the final gage producing a thin superficial carbonizatmn of its surface.

11. The process of making iron or steel wire, comprising drawing a wire to a desired gage, and at any. desired stage in the manufacture of the wire producing a thin superficial carbonization of its surface in a hot liquid medium.

12. The process of making iron" or steel wire, comprising drawing a wire to a de: sired gage, and at any desired stage in the manufacture of theiwire prior to drawing to the final gage producing a thin superficial hardening of its surface.

.In witness whereof, I have hereunto set my hand at Muncie, Indiana, this twentysecond day of February, A. D. one thousand nine hundred and twenty-four.

FREDERICK M. CRAPO. 

